Halperin, et al., CPR Chest Compression Monitor, U.S. Pat. No. 6,390,996 (May 21, 2002) discloses a CPR chest compression monitor which uses a compression sensor, e.g. an accelerometer, to measure acceleration of a patient's chest wall due to CPR compressions to calculates the depth of compressions based on acceleration signals provided by the accelerometer.
Palazzolo, et al., Method of Determining Depth of Chest Compressions During CPR, U.S. Pat. No. 7,122,014 (Oct. 17, 2006) discloses the use of a chest compression monitor with a chest compression device, such as the AutoPulse® chest compression device, with an accelerometer in the belt, and an accelerometer fixed to the supporting surface is used as a reference sensor.
Halperin disclosed a compression monitor, e.g. comprising an accelerometer and a control system for processing accelerometer signals to determine the depth of chest compressions accomplished in the performance of CPR. In the systems proposed by Palazzolo, this system is improved with the addition of a reference sensor, which can be a second compression monitor or accelerometer. Systems that use a compression sensor with or without a reference sensor can be further improved to provide accurate measurement of chest compression depth.